How do you solve Determine if a Cell Is Reachable at a Given Time on LeetCode?

Determine if a Cell Is Reachable at a Given Time (LeetCode #2849) can be solved using Brute Force or Optimal Solution. The optimal approach is Optimal Solution with O(1) time complexity and O(1) space complexity. Key insight: The Chebyshev distance is crucial for determining the minimum time required to reach the target cell.

What is the time complexity of Determine if a Cell Is Reachable at a Given Time?

The optimal solution for Determine if a Cell Is Reachable at a Given Time runs in O(1) time and uses O(1) space. The optimal solution has constant time and space complexity due to the simple arithmetic operations involved.

What is the brute force solution for Determine if a Cell Is Reachable at a Given Time?

The brute force approach for Determine if a Cell Is Reachable at a Given Time is Brute Force, with O(1) time complexity and O(1) space complexity. The brute-force approach involves calculating all possible paths from the starting cell to the target cell and checking if any of them can reach the target in exactly 't' seconds. This method is straightforward but inefficient for large grids. The optimal Optimal Solution approach improves this to O(1).

What algorithm or data structure is used to solve Determine if a Cell Is Reachable at a Given Time?

Determine if a Cell Is Reachable at a Given Time uses the following concepts: Math. The recommended patterns to study are: Math, Grid Traversal.

What are the interview tips for Determine if a Cell Is Reachable at a Given Time?

Always clarify the problem constraints and edge cases with the interviewer. Explain your thought process clearly while solving the problem. Practice recognizing patterns like Chebyshev distance in grid-based problems.

What are common mistakes when solving Determine if a Cell Is Reachable at a Given Time?

Forgetting to check the parity of (t - distance) when distance is less than t. Misunderstanding the concept of Chebyshev distance and using Manhattan distance instead.

#2849

Determine if a Cell Is Reachable at a Given Time

Medium

MathMathGrid Traversal

LeetCode ↗

Approaches

Brute ForceOptimal

Complexity Comparison

	Brute Force	Optimal Solution★
Time	O(1)	O(1)
Space	O(1)	O(1)

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Intuition

Time O(1)Space O(1)

The optimal solution leverages the properties of the Chebyshev distance to determine if the target cell can be reached in exactly 't' seconds. This approach is efficient and avoids unnecessary calculations.

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Algorithm

3 steps

1Step 1: Calculate the Chebyshev distance between (sx, sy) and (fx, fy).
2Step 2: Check if the distance is less than or equal to 't'.
3Step 3: If the distance is less than 't', ensure that the remaining time (t - distance) is even to allow for backtracking.

solution.py9 lines

1# Full working Python code
2
3def isReachable(sx, sy, fx, fy, t):
4    distance = max(abs(fx - sx), abs(fy - sy))
5    return distance <= t and (t - distance) % 2 == 0
6
7# Example usage
8print(isReachable(2, 4, 7, 7, 6))  # Output: True
9print(isReachable(3, 1, 7, 3, 3))  # Output: False

ℹ

Complexity note: The optimal solution has constant time and space complexity due to the simple arithmetic operations involved.

1The Chebyshev distance is crucial for determining the minimum time required to reach the target cell.
2The parity of the remaining time after reaching the target distance is important for ensuring we can use the time effectively.

Solutions and explanations are original Tejav content. Problem titles © LeetCode — use the LeetCode button above for the full problem statement.